Intake manifold



R. C. STOLTE INTAKE MANIFOLD Sept. 4, 1956 5 Sheets-Sheet 1 Filed Jan. 15, 1955 wmu Mc m aw l ILIT Se t. 4, 1956 R. c. STOLTE 2,761,437

INTAKE MANIFOLD Filed Jan. 15, 1953 5 Sheets-Sheet 3 Vlllrllllldtlli will!!! INVENTOR ATTORNEYS R. C. STOLTE INTAKE MANIFOLD Sept. 4, 1956 5 Sheets-Sheet 4 Filed Jan. 15, 1953 94%4/4! ATi'QRNEYs R. c. STOLTE INTAKE MANIFOLD Sept. 4, 1956 5 Sheets-Sheet 5 Filed Jan. 15, 1953 ATTORNEYS United States Patent INTAKE MANIFOLD Richard C. Stolte, Birmingham, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 15, 1953, Serial No. 331,371

23 Claims. (Cl. 123-127) The present invention relates to charge forming means for engines and has particular relation to an inlet manifold for use with a multiplicity of carburetors for supplying explosive mixtures to an in-line engine or other internal combustion engine. I

One of the factors controlling the power available from an internal combustion engine is the volumetric efiiciency or the ability of the engine to ingest the gaseous fuel mixtures into the combustion chambers. The ability to draw these gaseous mixtures into the cylinders is limited by the resistance to flow presented by the distribution passages disposed between the fuel supplying means and the combustion chambers. In multicylinder engines requiring an induction system having long passages to distribute the mixtures to the cylinders, this becomes a serious problem. This is particularly true in engines employing an intake manifold having a single carburetor. In engines having both single and multiple carburetion, the intake manifolds have a system of distribution passages that communicate with the engine cylinders. These passages are frequently of different lengths and have curves of different proportions that cause the various cylinders to be charged with mixtures of different proportions and volume.

It is now proposed to provide an intake manifold that possesses a plurality of separate passages. Each passage communicates with only one cylinder or group of cylinders. This will reduce the resistance to the flow of fuel charges into the cylinders and increase the volumetric efficiency of the engine. The manifold is so constructed that all of the passages are substantially identical in all respects. This will not only result in identical flow resistances for each cylinder thus promoting a uniform volume of charges, but it will also permit identical mixtures to reach the cylinders. A fuel supplying device such as a carburetor is associated with each of said passages to thereby further increase the volumetric efliciency.

Heretofore employing a multiplicity of carburetors on a single manifold has frequently resulted in unsatisfactory operation due to different conditions occurring in different portions of the manifold. These conditions may arise as a result of manufacturing tolerances, particularly in the carburetor and the associated throttle valves. Small variations in a butterfly valve such as those generally employed for throttle valves in an automotive engine wiil result in major variations in the operating characteristics of the valve when in a closed or nearly closed position. However, when fully opened the valves present substantially no limitation to the flow and accordingly any manufacturing errors will have little or no effect on the fluid flow. If such differences occur in a set of throttle valves on a single engine, there will be material variations in the charges delivered to the various cylinders at idling or slow speeds. This causes an objectionable roughness of operation.

It is, therefore, proposed to provide balance passages in the intake manifold that communicate with adjacent pairs of intake passages. These balance passageshav'e diameters that are substantially smaller than the diameters of the intake passages and will only compensate for the limited differences that occur at low speed throttle settings. To compensate for difierences that occur at or near full throttle, the throttles are actuated by a common adjustable linkage. The linkage is provided with means that allow radial adjustment of all the throttles so that they will all be in the same position at the same time.

Referring to the drawings:

Figure l is a side elevational view of an in-line six cylinder engine embodying the present invention.

Figure 2 is a plan view with parts thereof being broken away to show the interior of the engine head and how the manifold cooperates with the Siamese intake ports to charge the cylinders.

Figure 3 is an end view of the engine, a portion thereof being broken away, substantially along the plane of line 33 of Figure l to show the engine induction system.

Figure 4 is a bottom view of the central portion of the intake manifold taken substantially along the plane of line 44 of Figure 1.

Figure 5 is a plan view of the central portion of the intake manifold, a portion thereof being taken away to show the disposition of the balance passages and the exhaust ducts.

Figure 6 is a cross-sectional view taken substantially along the plane of line 66 of Figure 5.

Figure 7 is a side elevational view of an intake manifold embodying the present invention, portions thereof being broken away to more clearly show the exhaust ducts and balance passages.

Figure 8 is a view of a portion of the throttle control linkage.

Figure 9 is a perspective view of a part of one of the universal joints embodied in the throttle control linkage.

The engine 20 presently employed for practicing the invention is an in-line six cylinder internal combustion engine especially applicable for the operation of motor vehicles. The engine 20 includes a block 22 having a row of vertical cylinders 24 spaced longitudinally of the engine 20 and extending therethrough. The cylinders 24 starting at the front end of the engine 20 and proceeding to the rear are referred to as A, B, C, D, E and F, respectively. Water passages 26 for cooling are disposed in the block 22 in heat exchanging relation with the cylinders 24. The block 22 has a head 28 secured to the top thereof by any suitable means. The head 28 has a plurality of cavities 30 formed in the lower surface that are positioned to register with the openings 31 formed in the block 22- by the cylinders 24.

These cavities 30 form firing chambers 32 and cooper: ate with the surfaces 34 on the upper ends of the pistons 36 to form combustion chambers 38. A series of staggered openings 42 extend through the head into the firing chamber 32 to form a pair of valve seats 44 and 46 in each combustion chamber 38. Inlet valves 48 and exhaust valves are disposed in the openings 42. One inlet valve 48 and one exhaust valve is disposed in each firing chamber 32 to control the flow of gases into and out of the combustion chambers 38. The exhaust valves which control the outgoing flow of exhaust gases communicate with exhaust passages 52 that extend horizontally through the head 28 to form exhaust ports 53 in the side of the head 28. An exhaust manifold 54 is secured on the side of the engine 20 by a plurality of bolts 56. The manifold 54 is provided with spaced openings 58 that are positioned to register with the exhaust ports 53 in the head 28 and to collect the gases discharged therefrom in a common chamber'60.

, The center of this chamber 60 is provided with a heat v 3 box 62 that has an opening 64 in the top thereof and a fitting 66 on the bottom. The fitting 66 is adapted to receive the exhaust pipe 68 that discharges into the atmosphere. A thermostatically controlled heat valve 70 is positioned in the box 62 depending upon the operating condition of the engine 20, it will cause the hot exhaust gases to flow through the opening 64 in the top of the box 62 or directly into the exhaust pipe 68 where it is discharged into the atmosphere.

The intake valves 48 are of the so-called Siamese variety in which the valve seats for adjacent pairs of cylinders communicate with a common chamber 72 that is formed by an enlargement in the end of the intake passage 74. Each intake passage 74 extends horizontally inwardly from spaced intake ports 76 on the side of the head 28.

Both the intake and exhaust valves have stems 78 that extend upwardly to project through the top of the head 28. A plurality of rocker arms 80 are pivotally mounted on a shaft 82 extending longitudinally of the head 28. One end of each arm 80 engages a valve stem 78 while the other end engages a push rod 84 which is actuated by the engine cam shaft. 7

During the operation of the engine 20, the cam shaft will selectively lift the push rods 84 and cause the corresponding rocker arm 80 to depress the associated valve stem 78. This will open a valve and allow the desired gases to flow into or out of the combustion chamber 38. By employing a firingorder of A, E, C, F, B and D no two adjacent cylinders will fire one after the other and therefore only one cylinder 24 at a time will be charged through a single port.

The intake manifold which is preferably fabricated from a single cast piece may be secured in position on the side of the head 28 immediately above the exhaust manifold 54 by the same set of bolts 56 that are employed in mounting the exhaust manifold 54. The intake manifold 90 comprises an elongated member 91 that is provided with intake passages 92 that extend transversely therethrough for distributing the fuel to the cylinders 24. The passages 92 are all of the same size and are preferably of largediameter and short length. If any bends are required, they should be sweeping curves of large radius. Such a construction will materially reduce the resistance to flow and accordingly greatly assist in obtaining a high volumetric efliciency. The inside ends 94 of each intake passage 92 register with the intake ports 76 positioned on the side of the head 28. A separate carburetor 96 such as the side draft variety shown is employed for each passage 92. To prevent dirt and dust entering the engine, it is desirable that an air filter 98 be installed on each carburetor.

Balance passages 100 are formed to extend longitudinally of the member and interconnect adjacent pairs of intake passages 92. These passages may be formed by drilling lengthwise through the member 91 and closing the ends thereof with plugs 102. The diameter of the balance passages 100 should be large enough to maintain similar conditions during low speed operation but small enough not to interfere with high speed operation of the engine 20. This will result in the balance passages 100 having diameters substantially smaller than the diameters of the intake passages 92. It is also desirable that the lowest extremity of the balance passages 100 be above the bottom of the intake passage 92. Thus if any liquid fuel condenses out of the combustible fuel mixture, it will accumulate in the bottom of the intake passages 92 and therefore it will not impair the operation of the balance passages 100.

In order to assist in starting of the engine 20 and to facilitate operation thereof at low temperatures, means may be provided for heating the intake passages 92. This assists the engine 28 in rapidly reaching optimum operating conditions and prevents the liquid fuel from condensing out of the combustible fuel mixture. In the present instance these means include a pair of exhaust ducts 104 and 106 that are cast into the manifold 90. The core for the ducts 1G4 and 106 may be held in place through the openings 107 which are plugged during operation. The ducts 104 of the inner set are positioned closest to the engine 20 and are separated by a vertical partition 108. The ducts 106 of the second set are positioned farthest from the engine 20 and are also separated by the parti tion 108. The ducts 104 and 106 of both sets extend longitudinally of the manifold 90 and are separated. by a wall 110. Both sets of ducts have annular portions 112 that are disposed about the intake passages 92 in heat exchanging relation therewith. The wall has a window 114 in each end that allows gases to flow from one duct to the other. A riser 116 is positioned below the central intake passage 92 so as to register with the opening 64 through the heat box 62. The partition 108 is positioned so that the thermostatically controlled valve 70 under certain operating conditions can force the exhaust gases to flow up through the inlet vents 120 and down through the oulet vents 122 into the exhaust manifold 54. Thus it will be seen that during normal operation the exhaust gases will flow directly into the exhaust pipe 68 from the exhaust manifold 54. However, during cold conditions the heat valve 70 will deflect the hot gases through the exhaust ducts 104 and 106 to heat the intake manifold 90.

To control the engine 20 speed, butterfly throttle valves 128 are positioned in the discharge side of the carburetors 96 for controlling the amount of fuel mixture flowing into the intake passages 92. The position of all of the valves 128 is simultaneously controlled by a common linkage 130 which is actuated from the drivers compartment by means of rod 131. In order to prevent binding and to compensate for any axial misalignment which may be present between the shafts 132 of the butterfly valves 128, a plurality of universal joints 134 are employed.

. The universal joints 134 are placed at right angles to each other on opposite ends of the rods 136 and comprise a U-shaped member 138 that is secured to the end of the throttle shaft 132. The member 138 has a pair of elon gated openings 140 therethrough that slidably receives a hook 142 on one end of the rod 136. The hook 142 is retained in position by a spring 144 mounted between a pin 146 projecting from the hook 142 and one of the legs 148 of the U-shaped member 138. it will thus be apparent that as any expansion and contraction resulting from heating of the manifold 90 occurs, it is possible for the universal joints 134 to absorb any axial movement of the rods 136. To insure that the throttle valves 128 are all in the same position at the same time, radial adjusting means 150 of any suitable character may be provided. In the present instance an enlarged ball 152 is positioned 111 a tapered socket 154. As the external not 156 is tightened on the socket 154, the ball 152 will be wedged into position and prevent any relative radial movement of the rods 136. However when the nut 156 is loosened, the throttle valves 128 may be moved relative to each until the engine 20 runs smoothly.

While but one embodiment of the present invention has been shown, it will be apparent to those skilled in the art that various .changes and modifications may be made without departing from the invention. it is, therefore, to be understood the foregoing description is to be considered as illustrative only and in no way restrictive, reference being had to the appending claims to determine the scope of the invention.

What is claimed is:

1. Charge forming means for an'engine having different groups of cylinders charged through intake ports, said means comprising an intake manifold having a plurality v of substantially uniformly spaced intake passages extending therethrough, each of said intake passages being po- SltlOIlCd in said manifold to communicate with only one of said ports, a multiplicity of fuel supplying means mounted on said manifold, each of said fuel supplying means discharging into one of said intake passages, balance passages disposed in said intake manifold and communicating with adjacent pairs of said intake passages, said balance passages having diameters substantially smaller than the diameters of said intake passages, throttle means associated with each of said fuel supplying means and being positioned to control the amount of fuel discharged into said intake passages, and adjustable linkage means for actuating said throttle means.

2. Charge forming means for an engine having different groups of cylinders charged through common ports, said means comprising an intake manifold having a plurality of substantially equally spaced intake passages extending therethrough, each of said intake passages being positioned in said manifold to communicate with only one of said ports, a multiplicity of fuel supplying means mounted on said manifold, each of said fuel supplying means discharging into one of said intake passages, balance passages disposed in said intake manifold and communicating with adjacent pairs of said intake passages, said balance passages having diameters substantially smaller than the diameters of said intake passages, throttle valves disposed in each of said fuel supplying means and being positioned to determine the amount of fuel discharged into said intake passages, control means for actuating said throttle valves, said control means including a linkage having adjusting means adapted to simultaneously position all of said throttle valves in the fully open positions, and exhaust ducts formed in said intake manifold and communicating with the engine exhaust means, said ducts being positioned to conduct the hot engine exhaust gases into heat exchanging relation with said passages.

3. Charge forming means for an engine having different groups of cylinders charged through intake ports, said means comprising an intake manifold having a plurality of substantially uniformly spaced intake passages extending therethrough, each of said intake passages being positioned to communicate with only one of said intake ports, a multiplicity of fuel supplying means mounted on said intake manifold, each of said fuel supplying means discharging into one of said intake passages, balance passages communicating With adjacent pairs of intake passages, said balance passages having diameters substantially smaller than the diameters of said intake passages, butterfly valves positioned in each of said fuel supplying means to throttle the amount of fuel discharged into said intake passages, and a linkage coupled to each of said butterfly valves, said linkage including radially adjusting means adapted to determine the relatively angular displacement of said butterfly valves.

4. Charge forming means for an engine having different groups of cylinders charged through common ports, said means comprising an intake manifold having a plurality'of substantially equally spaced intake passages extending therethrough, each of said intake passages forming only one outlet positioned to communicate With only one of said ports, a multiplicity of fuel supplying means mounted on said intake manifold, each of saidfuel supplying means discharging into one of said intake passages, balance passages communicating with adjacent pairs of said intake passages, said balance passages having diameters substantially smaller than the diameters of said intake passages, butterfly valves positioned in each of said fuel supplying means to throttle the amount of fuel discharged into said intake passages, and a linkage coupled to each of said butterfly valves, said linkage including radially adjusting means adapted to control the relatively angular displacement of said butterfly valves, and exhaust ducts formed in said manifold and being positioned in heat exchanging relation with said passages.

5. Charge forming means comprising the combination of an engine having difierent groups of cylinders charged through common ports, said means comprising an intake manifold secured to said engine and having a separate intake passage for each port extending substantially transversely therethrough, each of said intake passages being positioned to communicate directly with only one of said ports, a multiplicity of fuel mixing means mounted on said manifold and discharging into one of said intake passages, throttle means for controlling the amount of said discharge, exhaust duct means positioned in said intake manifold in heat exchanging relation with said passages, an exhaust manifold mounted on said engine to collect hot exhaust gases, and means adapted to divert said hot exhaust gases through said duct means under certain operating conditions.

6. Charge forming means comprising the combination of an engine having different groups of cylinders charged through intake ports, said means comprising an intake manifold secured to said engine and having a separate intake passage for each of said ports extending substantially transversely therethrough, each of said intake passages being positioned to communicate directly with only one of said intake ports, a multiplicity of fuel mixing means mounted on said manifold and discharging into one of said intake passages, throttle means for controlling the amount of said discharge, exhaust duct means positioned in said intake manifold in heat exchanging relation with said passages, inlet and outlet means positioned in said intake manifold to communicate with said duct means, and means adapted to divert the exhaust gases into said inlet means under certain operating conditions.

7. Charge forming means comprising the combination of an engine having different groups of cylinders charged through common ports, said means comprising an intake manifold secured to said engine and having intake passages extending substantially horizontally therethrough, each of said intake passages being positioned to communicate with one of said ports, a multiplicity of fuel mixing means mounted on said manifold and discharging into one of said intake passages, throttle means for controlling the amount of said discharge, a pair of communicating exhaust ducts positioned in said intake manifold in heat exchanging relation with said passages, an inlet positioned in said manifold to communicate with one of said exhaust ducts, an outlet positioned in said manifold to communicate with the other of said exhaust ducts, an exhaust manifold mounted on said engine to collect hot exhaust gases, and valve means positioned in said exhaust manifold to simultaneously divert exhaust gases into said inlet and also to permit said exhaust gases to be discharged back into said exhaust manifold under certain operating conditions.

8. Charge forming means comprising the combination of an engine having difierent groups of cylinders charged through common ports, said means comprising an intake manifold secured to said engine and having intake passages extending substantially horizontally therethrough, each of said intake passages being positioned to communicate with one of said ports, a multiplicity of fuel mixing means mounted on said manifold, each of said means discharging into one of said intake passages, throttle means for controlling the amount of said discharge, a pair of communicating exhaust ducts positioned in said intake manifold in heat exchanging relation with said passages, an inlet positioned in said manifold to communicate with one of said exhaust ducts, an outlet positioned in said manifold to communicate with the other of said exhaust ducts, an exhaust manifold mounted on said engine to collect hot exhaust gases, and a thermostatically controlled valve disposedin said exhaust manifold and being adapted to simultaneoulsy divert the exhaust gases into said inlet and to allow said outlet to discharge said gases into said exhaust manifold under certain operating conditions.

9. An intake manifold for an engine having different groups of cylinders, said manifold comprising a plurality of substantially parallel equally spaced intake passages, each of said intake passages being adapted to communicate with one of said groups of cylinders for separately supplying different charges of combustible fuel mixtures to each of said groups of cylinders for operating said cylinders, and balance passages positioned in said manifold to interconnect adjacent pairs of said intake passages, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages.

10. An intake manifold for an engine having different groups of cylinders, said manifold comprising a plurality of substantially equally spaced intake passages, each of said intake passages being disposed entirely transverse of said manifold and adapted to communicate with one of said groups of cylinders for separately supplying different charges of combustible fuel mixtures to each of said groups of cylinders for operating said cylinders, balance passages positioned in said manifold to communicate with adjacent pairs of said intake passages, the inside diameters of said balance passages being substantially smaller than the inside dameters of said intake passages, and exhaust means disposed in heat exchanging relation to said intake passages.

11. An intake manifold for an engine having different groups of cylinders that are charged through common intake ports, said intake manifold comprising generally parallel intake passages having substantially identical proportions, each of said intake passages being positioned transversely of said manifold to communicate with only one of said intake ports and to separately supply different charges of combustible fuel mixtures to each of said intake ports for operating said cylinders, interconnecting balance passages positioned in said intake manifold to communicate with adjacent pairs of said intake passages, and walls positioned to form heating ducts disposed substantially parallel to said balance passages and being positioned to conduct hot gases into heat exchanging relation with each of said intake passages.

12. An intake manifold for an engine having difierent groups of cylinders that are charged through common intake ports, said intake manifold comprising a plurality of substantially equally spaced intake passages, each of said intake passages being positioned entirely transversely of said manifold to communicate with only one of said intake ports for separately supplying different charges of combustible fuel mixtures to each of said intake ports for operating said cylinders, interconnecting balance passages positioned to intersect adjacent pairs of said intake passages, said balance passages having inside diameters substantially smaller than the inside diameters of said intake passages, and walls positioned in said manifold to form heating ducts disposed substantially parallel to said balance passages and being positioned to conduct hot exhaust gases into heat exchanging relation with said passages.

13. An intake manifold for engines having a plurality of cylinders, comprising an elongated member having a plurality of substantially equally spaced intake passages extending transversely therethrough, each of said intake passages forming only one outlet positioned to supply separate charges of combustible fuel to said cylinders, balance passages formed longitudinally in said member and intersecting said intake passages intermediate their ends, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages, and exhaust ducts extending longitudinally of said member and being positioned in heat exchanging relation to said passages.

14. An intake manifold for engines having a plurality of cylinders, comprising an elongated member having a plurality of substantially equally spaced intake passages extending transversely therethrough, each of said intake passages forming only one outlet positioned to supply separate charges of combustible fuel to said different groups of cylinders, balance passages formed longitudinally in said members and intersecting said intake passages intermediate their ends, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages, and walls disposed longitudinally of said member to form exhaust ducts extending substantially parallel to said balance passage and being positioned in heat exchanging relationship with said passages.

15. An intake manifold for engines having different groups of cylinders, said manifold comprising an elongated member adapted to be mounted on said engine, intake passages extending transversely through said member and being positioned to supply separate charges of combustible fuel to each of said groups of cylinders, said intake passages having substantially identical proportions, balance passages formed longitudinally in said elongated member and intersecting said intake passages intermediate the ends thereof, and Walls positioned longitudinally of said elongated member to form a pair of exhaust ducts, each of said exhaust ducts having portions thereof in heat exchanging relation with said passages, said walls having openings therethrough to allow said ducts to communicate with each other.

16. An intake manifold for engines having different groups of cylinders, said manifold comprising an elongated member adapted to be mounted on said engine, intake passages extending transversely through said elongated member and being positioned to supply separate charges of combustible fuel to said ditferent groups of said cylinders, balance passages formed longitudinally in said elongated member and intersecting said intake passages intermediate the ends thereof, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages, first exhaust duct means formed longitudinally in said elongated member and having portions thereof disposed in heat exchanging relation with said passages, second exhaust duct means formed longitudinally of said elongated member and having portions thereof in heat exchanging relation with said passages, and conduit means positioned in said elongated member to communicate between said first and second exhaust duct means.

17. An intake manifold for an engine having different groups of cylinders that are charged through common intake ports, said intake manifold comprising a plurality of substantially parallel intake passages, each of said intake passages being positioned in said manifold to communicate with one of said intake ports for separately supplying different charges of combustible fuel mixtures to each of said intake ports for operating said cylinders, interconnecting balance passages positioned to intersect adjacent pairs of said intake passages, said balance passages having inside diameters substantially smaller than the inside diameters of said intake passages, first exhaust duct means formed longitudinally of said elongated member and having portions thereof in heat exchanging relation with said intake passages, second exhaust duct means communicating with said first exhaust duct means and being formed longitudinally of said elongated member to have portions thereof in heat exchanging relation with said passages, inlet means in said manifold being positioned to divert 'hot exhaust gases into one of said exhaust duct means under certain operating conditions, and outlet means communicating with the other of said exhaust duct means and being efliective to return the exhaust gases to said exhaust system.

18. An intake manifold for an engine having different groups of cylinders that are charged through common intake ports, said intake manifold comprising substantially parallel intake passages horizontally disposed in said manifold to communicate with only one of said intake ports for separately supplying different charges of combustible fuel mixtures to each of said intake ports for operating said cylinders, balance passages having inside diameters substantially smaller than the inside diameters of said intake passages, said balance passages being positioned to intersect adjacent pairs of said intake passages so that the lower extremities of said intake passages are below the lower extremities of said balance passages, and exhaust duct means disposed in heat exchanging relation with said passages.

19. An intake manifold adapted to be secured to an engine having a plurality of cylinders charged through intake ports, said manifold having a plurality of transverse intake passages extending directly therethrough from the opposite sides thereof, one end of each of said passages forming an outlet in one side of said manifold for communicating with only one of said intake ports to supply charges of combustible fuel mixture to said cylinders, the other end of each of said intake passages forming inlets in the opposite side of said manifold for communicating with individual fuel mixing means mounted on said manifold, and balance passages positioned in said manifold to interconnect adjacent pairs of said intake passages, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages.

20. An intake manifold adapted to be secured to an engine having a plurality of cylinders charged through intake ports, said manifold having pairs of openings disposed on the opposite sides thereof, one opening in each of said pairs forming an inlet and the other opening in said pair forming an outlet, said outlets being positioned to register with said intake ports when said manifold is secured to said engine, each of said inlets being adapted to communicate with individual fuel mixing means, a plurality of intake passages extending transversely through said manifold, each of said intake passages being positioned to directly interconnect an inlet opening and an outlet opening in one of said pairs, balance passages disposed longitudinally of said manifold to interconnect adjacent pairs of said intake passages, the inside diameters of said balance passages being substantially smaller than the inside diameters of said intake passages.

21. An intake manifold adapted to be secured to an engine having a plurality of cylinders charged through intake ports, said manifold having pairs of openings disposed on the opposite sides thereof, one opening in each of said pairs forming an inlet and the other opening in said pair forming an outlet, said outlets being positioned to register with said intake ports when said manifold is secured to said engine, each of said inlets being adapted to communicate with individual fuel mixing means, a plurality of intake passages extending horizontally through 10 said manifold, each of said intake passages being disposed in a vertical plane and having a reverse curve of relatively large radii to directly interconnect the inlet and outlet openings in said pairs, balance passages disposed longitudinally of said manifold to interconnect adjacent pairs of said intake passages.

22. Charge forming means for an engine having different groups of cylinders with each of said groups being charged through separate intake ports, said means comprising an intake manifold having a plurality of substantially identical intake passages extending therethrough with each of said intake passages communicating directly with only one of said intake ports, the outlet end of each of said intake passages being positioned to communicate with only one of said ports, a multiplicity of fuel supplying means mounted on said manifold, each of said fuel supply means being positioned to direct a combustible charge of fuel and air into the inlet end of one of said intake passages, and throttle means associated with each of said fuel supplying means and being positioned to control the volume of said charge flowing through said intake passages and linkage means for simultaneously positioning all of said throttle means.

23. An intake manifold adapted to be secured to an engine having groups of cylinders with each of said groups being charged through a separate intake port, said manifold comprising an elongated member adapted to be secured to said engine, a plurality of substantially identical intake passages extending substantially transversely through said member, the opposite ends thereof of each of said passages forming a separate inlet and a separate outlet on the sides of said member, each of said outlets being positioned to register with only one of said intake ports when said member is secured to said engine, each of said inlets being adapted to receive individual fuel mixing means for directing individual combustible mixtures of air and fuel into and through said intake passages.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,800 Paton Aug. 23, 1932 1,926,019 Aseltine Sept. 12, 1933 1,929,637 Hall Oct. 10, 1933 2,001,669 Smith May 14, 1935 2,033,211 Tice Mar. 10, 1936 

